This application claims a priority based on Japanese Patent Application No. 2000-258990 filed on Aug. 29, 2000, the entire contents of which are incorporated herein by reference for all purposes.
The present invention relates to an ACC (adaptive cruise control) system for extracting information associated with a following distance between a vehicle and another vehicle leading the same from an image of the leading vehicle photographed with a camera and for controlling the following distance between the vehicles based on the information.
An ACC (adaptive cruise control) apparatus loaded on a vehicle (hereinafter referred to as xe2x80x9cmaster vehiclexe2x80x9d) sense is a distance between the master vehicle and another vehicle in front (hereinafter referred to as xe2x80x9cleading vehiclexe2x80x9d) and controls the engine and braking system of the vehicle to keep an appropriate following distance between vehicles. In order to sense the following distance between the master vehicle and the leading vehicle, (a) some ACC apparatuses employ a distance measuring device such as an electric wave radar or laser radar and (b) some ACC apparatuses employ image processing on an image photographed with a stereoscopic camera, single-lens camera or the like. As an example of the latter type (b), Japanese unexamined patent publication No. H6-229759 has disclosed a distance estimator for estimating the following distance between a master vehicle and a leading vehicle based on an image of the leading vehicle photographed with a single-lens camera from behind. A description on the distance estimator will follow.
In the distance estimator, vehicle image data representing an appearance (rear view) of each type of vehicles as viewed from behind the vehicle and vehicle width data are registered in advance. The distance estimator successively extracts images of a leading vehicle from images photographed with a single-lens camera and searches the registered data to get vehicle width data associated with the vehicle image data that matches the first extracted image out of the registered data. When the vehicle width data of the leading vehicle is obtained as a result of the search, the distance estimator thereafter calculates, every time an image of the leading vehicle is extracted, the following distance between the master vehicle and the leading vehicle based on the number of pixels in the horizontal direction constituting the extracted image, the vehicle width data of the leading vehicle, the horizontal angle of view of the single-lens camera and the number of the pixels of the image in the horizontal direction photographed with the single-lens camera.
In the case of the distance estimator disclosed in the Japanese unexamined patent publication No. H6-229759, there is a need for registering vehicle image data and vehicle width data of major types of vehicles when it is actually used. Since a great amount of data is registered when the vehicle image data and vehicle width data of major types of vehicles are thus registered, it takes a long time to search vehicle width data of the leading vehicle.
In order to provide a more practical ACC system, in a cruise control system according to the present invention, a geometric feature value extracted from an image pattern of a leading vehicle at a predetermined timing is set as a reference parameter value for feature value of subsequent image patterns of the leading vehicle.